In the past, loads weighing up to 35,000 pounds have been dropped from aircrafts at altitudes below 500 feet utilizing the combination of parachutes and retro-rockets to reduce the impact velocity of the load. Parachutes are the most efficient method for decelerating a mass or load to a velocity of about 70 feet per second, while below 70 feet per second the retro-rocket is the most efficient method to decelerate a mass or load to a near zero vertical velocity at ground impact. These parachutes and retro-rocket systems have been very successful in reducing the vertical velocity of a descending load to near zero at a distance just above the ground. On the other hand, most of these parachute and retro-rocket systems do not have any mechanism for counteracting the horizontal velocity of the load due to wind drift or the aircraft's horizontal movement. Accordingly, the load will typically hit the ground with a horizontal velocity and subsequently topple over.
Examples of these parachute and retro-rocket systems are disclosed in U.S. Pat. Nos. 2,560,445 to Jackson and 2,872,138 to Vogt.
Various load landing systems are known in the prior art which utilize pivotable retro-rockets. However, these load landing devices have several disadvantages.
For example, U.S. Pat. No. 3,116,901 to Stencel discloses a load landing device having four retro-rockets that are rotatable about a vertical axis for developing a net horizontal component of the thrust that will oppose the horizontal component of the relevant movement between the load and the landing surface. A disadvantage of the prior art Stencel apparatus is that the amount of pivotable adjustment of the retro-rockets depends on how its touchdown probe contacts the ground. Furthermore, the Stencel apparatus does not vary the amount of thrust depending upon the wind velocity. Accordingly, the Stencel device may under or over-compensate on the horizontal component causing the load to tumble upon contacting the ground.
Another example of a load landing apparatus is disclosed in U.S. Pat. No. 4,409,658 to Beusse which describes a vehicle which utilizes pivotable retro-rockets connected directly to the load. A disadvantage of the Beusse system is that the retro-rockets are mounted directly on the load and on landing can cause the grass or underbrush on the ground to ignite. Another disadvantage of the Beusse system is that the retro-rockets must be constantly reoriented to counteract both the horizontal and vertical velocity.
This invention addresses these problems in the art, along with other needs which will become apparent to those skilled in the art once given this disclosure.